There are several types of compound words derived from numbers.
The first type are derived adjectives of form number + measure. English examples would be 10-inch or four-year. In Croatian, they are spelled without a hyphen, and the second part must be a (relational) adjective. The first part is derived from the ‘compounding forms’ of numbers:
The linking vowel (-o- in most forms) appended to create the compound form is lost in rare cases when an adjective begins with a vowel; it’s not lost if the vowel is a part of the original number:
|desetinčni 10-inch||stoinčni 100-inch|
Despite being spelled as one word, they often pronounced with two places of stress, one on the number, another on the adjective. (You will occasionally see such adjectives in a non-standard spelling, as two words, or even with a hyphen, e.g. deset-inčni and deset inčni)
They are used as any other adjective:
Sutra počinje trodnevni festival. A three-day festival begins tomorrow.
Bili smo na dvotjednom odmoru. We were on two-week vacation.
With forms derived from numbers based on 10 (10, 20, 50, etc.) you’ll sometimes see forms without the vowel -o-, that is pedesetgodišnji besides usual pedesetogodišnji. You will also see non-standard forms derived from numbers 5, 6 and 7, like ones for 4, that is:
When such adjectives – derived from relative adjectives of time periods – are used with people and animals, they mean three-year-old, forty-year-old, etc. For example:
Dovela je šestogodišnjeg sina. She brought her six-year-old son.
Note that the words derived from šesto- can mean both 6- ans 600-; therefore, some people write compounds derived from 600- as šeststo-. In the real life, confusion is rare – there are very few 600-year-olds around.
The second type uses suffix -ak to create numbers (not adjectives!) that correspond to English -odd. They are formed only from ‘round’ numbers, such as:
The third type are nouns derived from smaller numbers using -ica and -ka (the derivation is not regular, forms must be remembered):
1 → jedinica|
2 → dvojka
3 → trojka
4 → četvorka
5 → petica
6 → šestica|
7 → sedmica
8 → osmica
9 → devetka
10 → desetka
They mean e.g. ‘digit two’, or colloquially, something with the number on it, e.g. a playing card, bus or tram – depending on the context:
Čekat ću šesticu. I’ll wait for a number 6 tram.
However nouns derived from 1, 3 and 4 have special meanings as well:
trojka three-person team
četvorka four-person team
(English sometimes uses a noun for the three-person team, taken from Russian: troika. You see it’s almost identical to Croatian.)
(the rest is coming soon)